Control release of prostaglandin E2 from polylactic acid microcapsules, microparticles and modified microparticles.

Low molecular weight polylactic acid (PLA) microparticles containing prostaglandin E2 were prepared. An average particle size of 30 micron was obtained by grinding at low temperature. These particles were further treated by heating to modify the shape and the release pattern. Microscopic studies showed that the modified particles had a smoother surface than the non-modified particles. The drug was also incorporated into PLA microcapsules using the solvent evaporation process, but the incorporation efficiency was lower. We studied the release profiles of modified particles prepared using different molecular weight PLA. The release rate depended on the molecular weight with lower molecular weights having a greater release rate. In addition, the release studies showed different matrix forms made from the same molecular weight PLA had different release patterns. For example, the microcapsules released the drug very slowly whereas the modified particles exhibited a moderate release rate. It was also noted that the matrix release model could describe the release patterns of microcapsules and modified particles very well. However, the release patterns of non-modified microparticles did not follow this model.